Chapter 2: The Network Interface

Chapter 2: The Network Interface

Nothing is more basic to network configuration than the interface the system uses to connect to the

network. On most Linux servers, the network interface is an Ethernet card. Yet Linux systems are

not limited to using Ethernet for network access. There are several types of network interfaces. One

widely used network interface is the computer's serial port. Linux provides excellent support for

serial−line communications, including a full range of tools to run TCP/IP over a serial line using

Point−to−Point Protocol (PPP).

This chapter begins the discussion of configuring a Linux system as a network server by looking at

how network interfaces are installed and configured. We begin with the Ethernet interface, which is

the most popular TCP/IP network interface, and then go on to discuss how the serial interface is

used for data communications. Finally, this chapter covers how PPP software is configured to turn

the serial port into a TCP/IP network interface.

Configuring an Ethernet Interface

A Linux Ethernet interface is composed of both a hardware adapter card and a software driver.

There are many possible brands and models of Ethernet cards. Select a card that is listed in "The

Linux Hardware Compatibility HOWTO" by Patrick Reijnen, or listed among the approved hardware

at your Linux vendor's website. When you find a card that works well for you, stick with it until you

have a good reason to change.

Loadable Ethernet Drivers

The Ethernet interface software is a kernel driver. The driver can be compiled into the kernel or can

be loaded as a loadable module, which is the most common way to install an Ethernet driver. On a

R e d H a t s y s t e m , t h e l o a d a b l e E t h e r n e t d r i v e r s a r e f o u n d i n t h e

/lib/modules/release/kernel/drivers/net directory, in which release is the kernel version number. A

directory listing of the network device drivers found on a Red Hat 7.2 system is shown in Listing 2.1.

Listing 2.1: Loadable Network Device Drivers

$ cd /lib/modules/2.4.7−10/kernel/drivers/net

$ ls *.o

3c501.o at1700.o eepro100.o ne2k−pci.o slhc.o

3c503.o atp.o eepro.o ne3210.o slip.o

3c505.o bonding.o eexpress.o ne.o smc−ultra32.o

3c507.o bsd_comp.o epic100.o ni5010.o smc−ultra.o

3c509.o cs89x0.o eql.o ni52.o starfire.o

3c515.o de4x5.o es3210.o ni65.o strip.o

3c59x.o de600.o eth16i.o ns83820.o sundance.o

8139too.o de620.o ethertap.o pcnet32.o sungem.o

82596.o defxx.o ewrk3.o plip.o sunhme.o

8390.o depca.o hamachi.o ppp_async.o tlan.o

ac3200.o dgrs.o hp100.o ppp_deflate.o tun.o

acenic.o dl2k.o hp.o ppp_generic.o via−rhine.o

aironet4500_card.o dmfe.o hp−plus.o ppp_synctty.o wavelan.o

aironet4500_core.o dummy.o lance.o rcpci.o wd.o

aironet4500_proc.o e1000.o lne390.o sb1000.o winbond−840.o

arlan.o e100.o lp486e.o shaper.o yellowfin.o